The easy solution is to put them in a plastic freezer bag, the kind that is re-sealable.

addendum: I'm assuming they are not carrying many cartridges. If there is concern for the bag life, double bag them. Change the bag whenever a hole or damage is noted on the outer bag. Start with fresh clean cartridges for each scout. Get rid of all the present ammunition in their possession.

Last edited by tw; 12/31/14 10:47 PM. Reason: addendum